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DW359 Circular Saw Sparking, smelling, eating brushes


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I have a DW359 that's been used very little over it's lifetime. I was just using it to make a few plywood cuts and I noticed the RPM of the motor slowing down. I took a look and saw pretty big sparks.  I stopped the saw, pulled the brushes and they looked worn. Ordered and installed new brushes. . still sparking like crazy and noticed the new brushes are already wearing and the motor still smelling after only a few seconds of running. Took a bit closer look and notice a small "hangup" on the brushes at a certain point each revolution of the "commutator" (if that's the right term) and looks like the new brushes are "chipped" at the ends! What is causing the excessive sparking and is there anything I can do, (sand, etc) to stop the brushes from getting knicked and chipped?


The saw is otherwise in great shape. I looked online and see the parts it needs, armature, etc. may not be available anymore. Is there anything I can do to see if I can get this baby running right again? Thanks in advance! 🙂

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Welcome to the forum.


In the old days there were wooden pencils w/ erasers on the end.


The wooden pencil eraser is a great tool for cleaning up the commutator.


Remove both brushes, rotate the armature while pressing the eraser against the commutator. Visually inspect the commutator while rotating the armature. It should be smooth and shiny. If required use a fragment of ~600 grit emery paper pressed against the hand-rotated commutator to attain smooth and shiny.


Then inspect / verify / correct all segment gaps to ensure they are clean and are not shorted.


Both brushes must slide freely within brush holders. If the brush end is not good then wrap fine emery paper around a socket having the same OD as the commutator and rotate the socket to clean up the brush end.



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Hey Wingless! Thanks so much for not only the Welcome but the awesome, quick response! I don't know all of the correct terminology but am pretty sure I understand what you're saying to do.


I can smooth out the outer surface of the commutator. Not exactly sure what I'm looking for regarding clean segment gaps and how to ensure that they're not shorted. Does that just mean that they're not touching each other?


The ends of the original brushes looked pretty good. The brushes themselves were worn short of course but looked okay. The reason I replaced them was that on one of them, the wire that connects the brush to the metal end-cap was broken so I'm sure it wasn't functioning. When I replace them with new brushes, the new ends weren't rounded off to match the curve of the commutator but squared off. Upon a few seconds of running and sparking, now they're broken-off on the ends and jagged. I'm guessing it's a new set of brushes at least that I'm looking at?


Anyway, I'll get that sucker apart and start what you suggested and I'll get some pictures posted as well. Thanks again so much for your help! 🙂

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